The present invention relates to interconnection between a multidimensional transducer array and electronics used for imaging.
Ultrasonic transducer arrays include a plurality of elements with opposing electrodes. One electrode is connected to ground. The other electrodes are connected to beamformer or system channels for generating transmit waveforms and receiving signals responsive to echoes. The transducer arrays are typically connected to the electronics of the beamformers with flexible circuits. Flexible circuits are single or double sided sheets of electrically insulating material, such as Mylar, with deposited electrical traces. Flexible circuits require space on both ends for termination, such as termination at the transducer array on one end and termination at the beamformer electronics or coaxial cables on another end. Due to the proximate location of the electrical traces and limited insulation, cross-talk may be introduced by dense flexible circuits. For multidimensional transducers, such as two dimensional arrays, the density of electrical traces on the flexible circuit may increase. Traces for the separate electrodes of the two dimensional array are forced to fit on one or two surfaces. The resulting increase and the pitch of the traces is finer than the pitch of the array elements being interconnected, increasing the risk of cross-talk. The elements of the two dimensional array may be small, resulting in a higher impedance. The effects of cross-talk may increase as a result.
One interconnection technique for multidimensional transducer arrays is a z-axis interconnect. A plurality of electrical conductors is routed through backing block material along the z or range axis of the transducer. Other conductors then connect with the z-axis interconnects for electrical communication with the beamformer electronics. In one multidimensional transducer, a multiple layer printed circuit board, such as 48 layers of printed circuit board material, is formed and positioned adjacent to the z-axis interconnects of the multidimensional transducer array. Active electronics devices, such as beamformer circuitry, are provided on only two surfaces of the multiple layered printed circuit board. To provide more space for active electronics, the printed circuit board is lengthened or widened. The length of the conductive path from any two elements of the multidimensional transducer array to the active electronics may be different, causing a channel length mismatch and associated artifacts. The greater the difference in the lengths, the greater the artifacts that may be caused.